Conventionally, a diaphragm pump including a rapid-discharge-valve structural body is used to supply a pressurized gas to an object to be pressurized such as a hot water heater or sphygmomanometer. In the diaphragm pump of this kind, the rapid-discharge-valve structural body is installed in the discharge port of the diaphragm pump. As described in patent literature 1, when the diaphragm pump stops after pressurized air is supplied to an object to be pressurized, the rapid-discharge-valve structural body instantaneously decreases the pressure remaining in the object to be pressurized to the atmospheric pressure. FIG. 5 shows an example of this rapid-discharge-valve structural body.
A rapid-discharge-valve structural body 200 shown in FIG. 5 includes a vessel 210, a valve body 220 formed in the vessel 210, and a spring 230 for biasing the valve body 220.
The vessel 210 includes a supply port 211 to which air is supplied, a discharge port 212 for supplying air to an object to be pressurized, and an exhaust port 213 for exhausting air from the vessel 210. The valve body 220 is formed in the vessel 210, and partitions the internal space of the vessel 210 into an input-side space 214 connected to the supply port 211, and an output-side space 215 connected to the discharge port 212 and exhaust port 213. The valve body 220 includes a valve main body 221 for selectively closing the supply port 211 and exhaust port 213, a support portion 222 for supporting the valve main body 221, and a communication passage 223 for allowing the input-side space 214 and output-side space 215 to communicate with each other. The spring 230 biases the valve main body 221 toward the supply port 211.
In the rapid-discharge-valve structural body 200 configured as described above, when air is supplied from a pump chamber of the diaphragm pump to the supply port 211, air pushes up the valve main body 221 closing the supply port 211, and enters the output-side space 215 from the input-side space 214 through the communication passage 223. In this state, a pressure loss is generated because air flows through the communication passage 223, and the internal pressure of the input-side space 214 becomes higher than that of the output-side space 215. When the difference between the pressure of the input-side space 214 and that of the output-side space 215 becomes higher than the resilient force of the spring 230, the valve main body 221 closes the exhaust port 213, thereby disconnecting the discharge port 212 and exhaust port 213. Accordingly, air supplied to the supply port 211 is supplied from the discharge port 212 to the object to be pressurized.
On the other hand, when the supply of air to the supply port 211 is stopped by stopping the diaphragm pump, the communication passage 223 decreases the difference between the internal pressure of the input-side space 214 and that of the output-side space 215. Consequently, the resilient force of the spring 230 pushes down the valve main body 221 toward the supply port 211, thereby connecting the discharge port 212 and exhaust port 213. Therefore, the internal pressure of the output-side space 215 connected to the object to be pressurized through the discharge port 212 becomes the atmospheric pressure.